Second dual preset pressure relief valve

摘要

Described herein is a pressure relief valve that vents contents from a rail tank car or similar container at two preset pressures. The lower preset pressure is attained whenever specific valve attachment devices melt well below the spontaneous combustion temperature of the contents of a rail tank car or similar container. When these attachment devices melt, formerly attached corresponding constant force spring assemblies disconnect from a spring plate. Without these operative attached spring assemblies there is less force to oppose the pressure from the contents of rail tank car or similar container. With less opposing force, the contents of the rail tank car or similar container escape from under a dislodged sealing disk before the rail tank car or similar container (i) over pressurizes and causes the tank shell to fail or (ii) the contents self-combust, and both of which events cause an explosion.

主权项

1. A dual preset pressure relief valve comprising valve components by which said pressure relief valve can relieve pressure from contents within a rail tank car or closed container or at a first temperature and a second temperature,
said valve components comprising constant force spring assemblies, a spring plate and mechanical attaching components, said mechanical attaching components attaching said constant force spring assemblies to said spring plate, said mechanical attaching components comprising a first plurality and a second plurality, said second temperature being the melting temperature of a second material, said second plurality of said mechanical attaching components comprising said second material, said melting temperature of said second material being lower than the melting temperature of said first plurality, said second plurality disconnecting from said spring plate and said constant force spring assemblies at said melting temperature of said second material, said first plurality remaining connected to said spring plate and said constant force spring assemblies at said melting temperature of said second material.